The most common and most likely answer to this crossword clue is the 9 letter word PANICKING
I've seen this crossword clue in The Times
P
A
N
I
C
K
I
N
G
Buddy explains!

The straight part
We know that "going to pieces" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case going to pieces = panicking.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does PANICKING mean?
PANICKING verb- To feel overwhelming fear.
- To cause somebody to panic.
- (by extension) To crash.
- (by extension) To cause the system to crash.